That 'Literating Spade

"Under my window, a clean rasping sound
When the spade sinks into gravelly ground:
My father, digging. I look down"

The image of Seamus inside, at his window, looking down upon his father digging into the "gravelly ground," reinforces the main contrast of the poem: Seamus works inside with a pen, while his father works outside with a spade. The alliteration in the stanza, "spade sinks" and "gravelly ground," is connected with the description of his father working below in the field, not with him at the window writing. This might seem odd: alliterations are the tools of authors, not diggers. Why then use them to describe his father?
Looking at his other clear use of alliteration in the poem in stanza 7, we see again that not to describe his writing but to describe his father's digging is alliteration used. "Squelch and slap of soggy peat" and "curt cuts" describe the world outside, not inside, and by using a literary tool to describe his father's work Seamus connects the pen more intimately with the spade. As the spade is reaching into the context of his writing, so his writing form is reaching into the digging of a spade. By applying his literary skills to the description of his father's trade, Seamus further defines the link between pen and spade, so that as the pen can dig, so can the spade alliterate.